Apparatus for ascertaining vision sensitivities



Dec. 10, '1940. H R. DE SHQ/A 222455@ APPARATUS FOR ASCERTAININGVISIN.ENSITIV'JITIES`r Filed Jne 22, 1938 5 Sheetsfhee't i2 ATTORNEYSDef; W, H. R. DE SILVA Z APPARATUS FOR ASCERTAINING VISION SENSITIVITIESFiled June 22, 1958 5 Sheets-Sheet 5 ATTOR N EYS @sa H. R. @a 5mm224,564

APPARATUS FOR ASCERTAINNG VISIONSENSITIVITIES Filed June 22, 195s 5sheefsnsheet 4 Y @Milk/i) 0 ATTORN EYS 5 sheets-sheet 5 H. R. ma slLvAFiled June 22, 1938 APPARATUS FOR ASCERTAINING -VIS-10H1SENSI'I'IVITIESDiern 10,1940.

INVENTO I R282 APPARATUS Fon AscnnTArNrNo. vrsroN sENslrrvn'ms Harry R.De'Silva, Cambridge, Mass. Application June z2, 193s, serial No. 215,198

14 Claims.

This invention relates to apparatus for ascertaining visionsensitivities of a human being.

More speciiically, the invention relates to a method and .apparatus forascertaining one or more vision sensitivities which are ordinarilyemployed when one operates a motor vehicle on a public highway. A

The invention has for its object generally the provision of proceduralsteps. together with suiti0 vision sensitivities desired 'to beascertained. More specincally, the invention has for its object theprovision of a combination of procedural steps together with coordinatedinstrumentalil ties for ascertaining one or more of the visionsensitivities which it is desired to ascertain of one who may operate amotor vehicle. i

Another object is to provide procedural steps and coordinatedinstrumentalities adapted for determinlnga desired s et of differentvision sensitivities of an operator of a motor vehicle on a publichighway which may be involved in both day and night driving.

Another obiect is to provide procedural steps and coordinatedinstrumentalities for determining the vision sensitivities ci anoperator of a motor vehicle on a public highway at night, such as glareblindness and glare recovery.

Another object is to provide procedural steps and coordinatedinstrumentalitles for ascertain-I ing a subjects general visualefficiency, such as visual keenness, speed oi perception, sensitivitytomotion, and depth perception.

`Another object is to provide apparatus for testing and registering withprecision the vision sensitivities of operators of motor vehicles whichis of acharacterthat may be installed in a testing device, such as acabinet, and includes equipment arranged in a Acompact and convenientmanner for giving a desired set of tests for ascertaining visionsensitivities, such equipment being either conventional or speciallydevised.v Still another .object is to provide testing apparatus oi thecharacter indicated with an electric network which incorporates suitablecircuits --for coordinating measuring instruments with stimuli givingdevices for registering and indicating the times of reaction to certainroad conditions involving vision sensitivies and reaction by operatorsoi' motor vehicles. -Other objects oi the invention will inpart beobvious and will in part appear hereinafter.

The invention accordingly comprises the iestures oi construction,combination oi elements,

pliiied in the construction hereinatier set forth, and the scope of theinvention will loe indicated in the claims.

For a fuller understanding of the nature and w objects of the invention,reference should be had able apparatus, for testing a subject for theand arrangement of parte, which will be exem-` to the following detaileddescription taken in connection with the accompanying drawings. in-

which:

Fig. 1 is a view. mainly perspective, showings cabinet incorporating aplurality oi means for I testing the vision of subjects, particularlythose who may operate motor vehicles, according to the invention;

Fig. 2 is a side elevational view of the apparatus, shown in Fig. 1,parts being broken away .10 in order to illustrate constructionaldetails thereof;

Fig. 3 is atop plan view, part of the casing being shown broken away, inorder to illustra details of the interior construction: 15

Fig. i is an end elevational view of the apparatus, a portion of. theend wall vbeing broken away, in order to show other interiorconstructional details;

t Fig. 5 is an end e1evat1ona1v1ew'of theappa.- zo

ratus seen from the end lother than that shown in Fig. 4; A

Fig. 6 is a perspective view ci an electric motor assembly employedfortiming Vvisual reactions, indicating the period required for recoveryfrom certain conditions and determining the period ofthetest: Fig. 7 isa view showing another electric motor assembly, employed for testing formotion sensitivity; ,m

Fie'. 8 is a view, mainly diagrammatic,v showing ghe Awiring arrangementof the motoroi'- Fig.; v Fig.- 9 is a perspective view showing details'ci a `switching device advantageously employed in the network of theinvention; and Figs; 10 and 10a are diagrammatic views oi an exemplaryelectric network, and an exten- 'sion thereof, provided in accordancewith the invention. f* o In order to ascertain clinically, as proposedby the invention, a desired group of vision sensi-` tivities of asubject, particularly those deemed ordinarily employed when operating amotor ve' hicle under conditions encountered in both day a and nightdriving, the subject is submitted-to artificial conditions simulating asuitable held oi vision, such as that' encounteredv when drivingy on ahighway, and appropriate stimuli for vi-y sion reactions applied.

The clinical procedure involves es n first procedural step, submittingthe suhpect to the artincial conditions which would call into play adesired vision sensitivity ci a subject, auch as when operating a motorvehicleon a highway. g5 As a second procedural step, one or more controllable stimuli are generated for appropriate periods in a manner thatmay he perceived by the subject. 'Ihe thirdproced involves registeringfor the exclusive use of one 6o giving the test (hereinafter referred toas the tester) by means of an automatically set index on the controlmeans the intensity of a stimulus given. Where time intervals are theindex means one registers the instants of starting and stopping thestimulus whereby the intervening period o! time becomes the measure ofthe sensitivities involved The procedural steps above described areadvantageously administered by means of suitable apparatus providing theartificial conditions, which apparatus may be conveniently in the formof a cabinet adapted to be stationarily installed in a laboratory ortesting room and before which the subject is seated for testing. To thisend, suitable devices for simulating the driving conditions and givingthe stimuli desired are incorported in the apparatus. For example, aroad scene may be simulated and a stimulus, such as 20 a signal light,flashed for variable periods until 1 the subject indicates that he (orshe) has perceived the stimulus.

Such apparatus may be provided with means speciiically adapted to givestimuli for practicing procedural testing steps whereby the followingvision sensitivities may be ascertained:

1. Glare blindness; 2. Glare recovery; 3. Movement sensitivity; 4. Speedof perception; 5. Tunnel vision; 6. Visual coordination; 7. Depthperception; 8. Visual keenness; 9. Astigmatism; and

10. Color sensitivity.

To ascertain the glare blindness of a subjectv when driving at night, heis submitted to an articial scene simulating driving conditions on aroad at night. A stimulus is then given, in which an object is made toappear on the' road scene,

with conditioning lights of a predetermined intensity projecting intothe subjects eyes, simulating, for example, a truck with glaringheadlights. Another object, preferably having directional markingsthereon, which the subject is tol-d to watch for, is then illuminatedwith light of an intensity which may be varied. The illuminationemployed may be initially of a relatively low value and is graduallyincreased, or it may be initially of a high value and graduallydecreased until the subject can no longer see it.. In the first case,the subject is instructed by the tester to signal when he perceives ytheposition of the lines on the object; in the second, ihe signals when hecan no longer see them. The increase in the illumination required forthe subject to overcome his blindness is a measure of the subjects glareblindness.

To ascertain a subjects rate of recovery from glare when driving atnight, he is again submitted to an artificial road scene when an objectwith lights of predetermined intensity, such as an object simulating atruck with glaring headlights, is made to appear for a predeterminedperiod and then to disappear. The subject is again instructed to lookfor a dim object which simulates a pedestrian and requested to informthe tester when he can discern the direction of the markings on thepedestrian. Here, the object has a constant predetermined illumination.The period of time required for the subject to perceive the object is ameasure of his rate of recovery from 75 the glaring light initiallygiven.

In order to ascertain a subjects sensitivity to movement, he issubmitted to a scene containing a small object that -is moved laterallyat a very slow rate. The subject is instructed to watch it until henotices how the object moves and then 5 give a signal and tell thetester the direction of the motion which he perceived. The reciprocal ofthe period of time taken by the subject to determine the direction ofmovement may be taken as a measure of his movement sensitivity.

To ascertain a subjects speed of perception, the subject is submitted toanother scene, for example, a landscape oi' the character appearing on ahighway, and told to watch for the appearance of a marked object, suchas a pedestrian or 1D animal, which may appear somewhere in the scene.To generate this apparition, a suitable light source is flashed for avarying interval of time to illuminate the scene and object, the latterbeing conveniently provided as a reflection from a transparency over thescene. The interval is varied by the tester and is not to be longer thanneeded by the subject to get an impression on his retina. The subject istold to register as soon as he perceives the object by giving a signal.Such flash may begin with intervals as short, for example, as 0.001 of asecond which are gradually increased until the subject signals that hehas perceived -the object. The duration of the perceived signal may betaken as a measure of the subjects speed of perception.

To ascertain a subjects so-called tunnel vision, the subject is testedfor sensitivity to an object out of the direct line of vision which maybe moved through varying angles at the sides of the subjects eyes. Thereciprocal of the angle of displacement fromthe direct line of vision'may be taken as a measure of the subjects vtunnel vision.

To ascertain the subjects visual coordination, the vision of each eye isexamined separately. To this end, the subject is made to look at a pointsource of light. A Maddox rod, or other device of the character employedby oculists and opticlans for this purpose, is rotated in front of thesubjects eyes, The degrees of lateral or vertical imbalance may bemeasured in terms of degrees of displacement or separation, of the lightsource as viewed binocularly.

To ascertain a subjects judgment in perceiving depth, while seated atvarious distances, he is requested to pass judgment on the distancesfrom him of small objects in a judgment testing device which preferablycomprises a rotatable disk mounted to turn about a horizontal axis andhas distinguishable -objects thereon supported at varying distancestherefrom. 'I'he subject is told to name them in the order of nearness.The percentage of correct judgments may be taken as a measure of thesubjects ability to judge depth.

To ascertain a subjects' visual keenness, he is seated before a chartbearing rows of figures or letters of graded sizes, such as are commonlyused by oculists and Opticians. and asked to read the successivelysmaller rows from various distances starting with the greatest distance,which may be, for example, 40 feet. The several scores may be taken as ameasure of keenness.

As a further test for visual keenness, the two eyes may be testedseparately. To this end, the subject may be tested by putting on him apair of glasses whose right lens contains material to polarize all lighttransmitted in a vertical plane, while the left lens transmits lightpolarized in a horizontal plane. The tester holds a large sheet:reagisce of polarizing material in iront oi the chart bearing the rowsof iigures. By rotating the sheet the tester can make the subject seerespectively yiirst with his right and then with his left eye, The useof the polarizing material has the advantage of testing the right andleft eyes separately without the subject knowing which eye is tested andWithout subjecting either eye to the disturbing effect of covering oneeye.

To .ascertain astigmatic defects in a subjects vision, he is instructedto read a standard chart of the character ordinarily employed byoculists and Opticians for this purpose. The direction of blurred linesnoted by the subject indicates the astigmatic error of the'subjectseyes.

To ascertain a subjects color sensitivity, standard charts in colors aresubmitted, color blindness being detected by means of colored imagesmade of small dots or circles and disposed like the elements of a mosaicin a'background of a different color. On some charts, the iigures orimages are such that only the color-normal persons can perceive them,While in other charts the gures or images aresuch that only acolorblindperson will see them. The charts read are thus Aan index ofthe subiects ability to distinguish color.

Referring now to the drawings, and particulai-ly to A.'digs'. 1 to 5, acabinet is shown at l0 which preferably has one end closed, such endbeing denoted Ii. The cabinet has lenses in a suitable eye-shield i2disposed at the closed end for Viewing one or more scenes that arearranged within the cabinet. Such scenes are conveniently provided inassociation with screens, designated i3, M, and I5, respectively. Thesescreens are mounted on a partition in the cabinet and may be viewed by asubject seated outside the cabinet, when the screens are properlyilluminated from within.. By such means, an illusion is given,simulating driving under day or night conditions, as the case may be, ina manner which it is desired to apply to the subject for test purposes.

The other end i6 of the cabinet is preferably open and has disposed init one or more charts il that have standard opticians testing markingsthereon, for nipte, graded figures and/cr line groups ci' the d employedfor testing for astigmatism. Sicm'cle luminary lamps I8 are preferablymounted at the sides ci this end for illuminating the charts whendesired.

The space at the open end oi the cabinet not occupied by the charts mayadvantageously 'be utilized to accommodate some other testing device,for example, a depth perception testing device which has background diski9 that may be disposedbelow and in iront of the chart il. On top of thecabinet, in a suitable frame 20, is another oculists testing chart,such, for example, es a standard color testing chart. f

To equip the apparatus to make glare blindness and glare recovery tests,the screen' i3 is preferably arranged to simulate conditions whendriving on a highway at night, and has one or more objects arranged tobe illuminated with varying amounts of light. To this end, a truck isdepicted at 2i Aon the screen, which is provided with openings 2i havinglight projecting. lamps 22 disposed behind them so as to simulate theheadlights of the truck. Adjacent the object 2l is a second object 23arranged to simulate a diiierent forni, for example, a human form. Thisform is provided with a rotatable element 2i carrying contrastingdirectional l it markings, such as lines. Anilluminating means,simulating the subject-s headlights, is disposed in the cabinet, andadvantageously has the form of a light projector 2li thai-,has anadjustable light stop disk or lens carrier 25f and a lamp 26, connectedIin an electric circuit supplying current in a mannerhereinafterAdescribed. A knob 2l on the exterior of the cabinet has mechanicalconnections for rotating the disk 25' at will. A similar knob 28 on ashaft 28' is also provided for rotating the element 24 at will.

To measure the` time required by the-subject to recover from glare, thecabinet is preferably provided with suitable timing means, for example,a timing device having an' indicating hand 30 driven by a suitablemotor, such lmotor being also preferably arranged to control thecircuits which supply illuminating current to the lamps 22 and 26. Arelatively slow'synchronous motor may be employed for this purpose, suchas a 3 R. i?. M. singlephase synchronous motor, shown ai. M, in Fig. 6.The circuits which are automatically controlled by the' motor M aredescribed more fully hereinafter. The hand 30 is conveniently disposedto turnabout a dial mounted on a side of the cabinet, which alsomayconveniently have dials for rheostats for controlling the current ofthe lamps 22 and 26.

To equip the apparatus to make movement v sensitivity tests, screentageously arranged above the screen I3 so as to be viewed by the subjectmerely by raising his eyes, is provided with an opening through which isseen an object, such as a small white 'body 3l, to which is given a slowlateral movement. f To achieve such movement, the body 3I is mounted ona slowly moving carrier disk 32 that is preferably dark in color and ismounted for rotation on a; shaft 33 driven through worm gearing 34 bymeans of a reversible motor N. Any Suitable re, versible A. C.-rnotormay be employed. A re versible live-wire motor is convenient and is inthe form shown in Figs. 7, 8, and 10. To indicate clearly to the testerthe direction of motion being imparted to the body 3i, the motor shaft yis preferably extended through the casing and screen I5, which lattermay be also above screen I3 and adjacent to the screen i4. Screen I5 hasan opening through which a scene on a background plaque 36 is visiblethrough an obliquely disposed 'transparent member 31. The scene isilluminated by means of a lamp 38 placed behind a margin of the screenout of the range of the subjects vision. The object, for which thesubject is to watch, may be made to appear on the scene at 30 in randompositions by means of an image on a rotatable disk 30, mounted so as tohave its reflections projected by the member 3l into the subjects eyes.The position of the image is controlled by thedisk 39 which isaccordingly arranged for manipulation by the tester from without thecabinet by means of a knob 5d, as shown in Figs. 3 to 5. ,In thisarrangement, a second lamp 88 is provided to illuminate the image forshort periods, which may begin, for example, with periods of 0.001 oasecond and then lengthened at will. The timing of this illumination ispreferably automatically con- I4, which is advang" 4 assenso.

ample, adjacent to thel eye-shieldl"'so that the f subject whentcsted'therefor is required but to Y raise head'to look at `the fixationpoints, one

for the lett eyeandone' for theright eyelecated on 'the protractorboar-fl. Thefprotractor board is graduated with arcs at the sides toread angular degrees whereby sensitivity l'to an object moved by thetester about the periphery of thel arcs to various positions not intheline ofA vision lo may be determined and the objects position read indegrees of angular displacement from' such line by means of thejscalesmarked. on the pro--` tractor board.

Toequip the apparatus Ito maket'ests ior visual 12 coordination, avMaddox rod-"suitably mounted for use. for example, in a casing''.fisprovided f the drawings. The contact arms are shown piv-l 'votedrespectively at 1i and 'I2 and are connected" 1 f and associated withthe cabinet at aconvenient point. and mayha've a' mounting-finir:v4I',`I allfas l shown in Fig. 2. Such Maddox rod is. of course, g

used in themanner well ir'ncwnk in the art. The

source of light for `this test maybe provided in the cabinet, orextericrly when convenient.

depth perception, lthe movableudisk il at k'the l0 other end oi' thecasing has a pluraiityofobiects which may be in the form of large+headedpins.y

5 insertedtherein andvprojecting therefrom-at varying distances.

8l ous distances vfrom the cabinet andmaybe flabcled to distinguish themso as to be read in the light ofthe room where the test is'being-.conducted.y -Tovary the test. the dial:v i0. carrying the plus risarranged tolse-rotated at will byV di! the' tester. `To thisend, gearingItis provided.

to rotate the disk, the gearing being arranged for manual manipulationthrough a -ehaft I1 having a knob 48 on the exterior ci thecabinat. 'Ioequip the. apparatus tomate l.testszfior 45 visual'ireenness.astigmatism. and color sensitivity, 'charts are provided respectively atHand 2B, which are preferably the standard charts used for thispuma-:salas previously indicated; -Whcrej polarized light is to beemployed in making the 50 test. a suitable'pair'oi glasses or iframesvircuild-l E sitions and a manipulatinghandlefil, vwhich is.

preferably. mounted onta paneiloiithe .exterior of the cabinet"rfmoveinoiitbytho .tardif-lift` .i

A suitable haring circuito selectively set upby means. gangfaivitoh.handle i563 is 'Iii enormen page. lanacion, Hers., t5 f t switch isdepicted as being a ijlvepoaiti switch composed uiteten plaques. dusspectivelyti to Il, 'whichhava t'r'iu uns from which the several.circuit conm tiene lead, 'f5 These terminals are simultaneously 'swept.by

Vbl? handle 50.

These objectsizare arrangedI to be viewed -by the subject when seated atvarithe seven' contact arma (not shown in the draw`- ing ini theIinterests -oi' clearness-ot illustration), the arms being ganged.together for effecting 'such movement by means of a shaft l! that-isturned f The network here provided is preferably suppliedwith'alternating current in order torun l 'timing devices. -To this end.a pairof A.'C. `-"supply buses is shown at is. one ofwhich is-f "tappedby :means of a plurality or device sup# 1'0 plying or trunkingconductors denoted respectively 8| to 1li, the return from thedevicesfbeing effected inany convenient manner. for example,

vthrough ground, as illustrated in the drawings (the other supply busbeingsvhown as grounded 1`5- for this purpose) Trunking conductor Ii isshown as leading'tor a pair of contact arms of a relay, shown.generlallyat R.' Any suitable 'relay 'may-be employed. 1 for example, adouble-armed eight-'terminal re; 20

lay whose terminals iare designated "Il tofi'n" in parallel totheconductor Il. Thefcon'tact arms-arelmoved by the winding e 'connect'edggacross terminals 11 and 'Il when energized, the f arms swinging awayfrom the terminals '1I and To equip the apparatus i'or making tests forl15 into engagement with the terminals 1l and 1l. Current to energize therelay is normally'.

supplied to the terminal 11 by means of a con-.30 1 ductor :B leadingfrom the contact arm termi- `nal of! the plaque B2. The return fromtherelay n z-leadsrrom terminal .'18 to ground. A by-pass tor energizingthe relay at will is also provided in the formo!` a conductor 11ileading from 35 'the trunking conductor Il to the yterminal 11 which isnormally open but closed by a pushbutton. switch HD. thislatter beingconveniently mounted on .the cabinet for manipulation by the tester. .Aparallel branch of the trunking con- 40 ductorl 6l. designated 5i'.leads to one blade 80' -of a double-pole switch, indicated generally atSti, which is normally closed but arranged on the- ,.cabinet: atY aconvenient point for manipulation by thesubiect being tested.. Blade 80'when 45 closedengages. the terminal. of a conductor EN that leads to thefourth. terl'ninal on plaque 5i. A parallel branch BM is also tapped into the conductorliil for supplying current to lamp 23, dicpoeedin thecabinet for illuminating object Si, the return from which is grounded.The other blade Sii" of the switch 80 is connected by a conductor 13B toterminal 13 ofthe relay, the blade., $0" when closed engaging the termi`nal ola conductor 544 that leads to the fourth .55 contact terminal ofplaque 54. i

n V'Iruntdng conductor 62 is arranged to supply. a unilateral or. D. C.Vcomponent of current to motorfM. .It hence has in series with it a rec.

"tiiying device. shownk generally at S. From the d0 v rectiiyingdeviccthe circuit continues as conduct-or 52' leadingto terminal 8i ci' acircuit changing switch, shown generally at iii. 4 This llatter .has inaddition terminals Q2 and $3., the, 4

switch. blade being pivo'ted to terminal 83. From Ai515 terminal titithe circuit is continued as conduc tor t2" to a terminal or motor M, thereturn for which ley grounded. Inserted in thecircuit -iin aerien withthe switch and motor is a` suitable automatic motor controlling switch9i, such. for 70 cantonale, as a cani-actuated commutator switch.suitable constructionul details for such switch being shown in Fig. 9.Alternating current' for manning the motor is supplied to conductor 82by way ci conductor lili. In order that the,

motor M may be started at will by the tester, a by-pass about the switch9| is provided in the form of a conductor 89 which is connected betweenconductor 62 and a terminal of the motor M, the connection beingnormally open but arranged to be closed by a push-button switch 90 thatis in series with the connection but in parallel with the switch 9 IOther commutator switches are shown at 92 to 94 respectively andconnected in circuits, as hereinafter explained. Switches 9| to 94 areoperated by cams, denoted I0| to |04, respectively, the cams beingadvantageously disposed on a shaft 99 that extends from motor M to turnhand 30. Cam |0| actuates the operating arm of switch 9|, the cam havingan engaging periphery that moves the arm into circuit closing position.A notch in the periphery is provided into which the arm drops at the endof one revolution to open the motor circuit automatically. Cam |0I, inconsequence, is hereinafter referred to as the motor cam.

To supply unilateral or pulsating D. C. current to the motor N, aconductor 84 is connected from the terminal 8|, which is connected withrectier S, to one terminal ofthe ileld winding 81 of the motor N. Fromterminal 02 of this switch a second conductor 85 leads to'one terminalof another commutator switch 95 whose other terminal is also connectedto the adjacent terminal of winding 81 by way of conductor 85'. Thiscommutator switch is actuated by means of a cam |05 of the shaft drivenby motor N, as s hown in Fig. 7. Another by-pass conductor 86 forstarting purposes is connected between terminal 82 and conductor 85',this connection being normally open but closed by a push-button switch|06. Thus, it is seen that motor N may be started by the tester bydepressing switch |06, which is in parallel with the commutator switch95.

'Ihe circuits in the motor N are diagrammatl` cally illustrated in Fig.8 where it is seen that the eld winding 81 is arranged as the primary ofa transformer and has a secondary 91 whose terminals are connectedyrespectively to terminals |01 and |08 of a reversing switch whose blade|09 is connected to one terminal of shading windings 96 of the motor.The other end of the shading windings is connected to the mid-point ofthe secondary winding 91. By this arrangement, when switch |00 is indown-position, the held winding 81 may be energized with alternatingcurrent supply by conductor 85, the rectifier S being short circuited.Alternating current displaced in phase is also supplied to winding 96 inone direction or the other, depending on whether the blade |09 engageswith terminal |01 or with terminal |08, such directional phase displacedcurrent being had from one or the other of the two halves of secondarywinding 91 which are thus connected to impart a starting direction tothe motor rotor. The supply of running alternating current for the motoris had through the circuit comprisingconductors 5|, 6|', 80', 5|4, and5|0, andthenoe through switch |00, terminal 82, conductor 85, switch 95when closed, conductor 85', and winding 481 which is grounded. If thiscircuit be interrupted, vas by opening switch 80, the short aroundrectifier S is removed and a D. C. component of current passes in thecircuit comprising conductor 62, rectifier S, terminal 8|, a r 1dconductors 84 and 85 to winding 81 which is""g` 'runded. This componentoperates to effect the dynamic braking of motor N and avoid sofcalledovershooting ,on plaque 55.

Trunking conductor 63 leads to one terminal of the second operatedcommutator switch 92, whose other terminal has a plurality of parallelconnections, namely, 5|I, 5|2, and SH3, leading respectively to thefirst, second, and fifth terminals on plaque 5|, there being also afourth conductor 630 leading to terminal 16 of the relay R. Conductor 5l 0 leads from the contact arm terminal of plaque 5| to a point onconductor 82' in order to supply current for running motor M. A4conductor 63| is connectedA to conductor 630 and leads through parallelbranches to the first and second terminals respectively on plaque 56.

Another conductor 634 is also connected between terminal 14 of the relayand the fourth terminal A conductor 580 leads from the contact armterminal of plaque 56 to one of the switch blades w-I of a four-bladeddouble-throw switch, shown generally at W. From one terminal of theswitch that is engaged by blade w-I when in up-position, a conductor 56|is led to a contact arm terminal of another relay, shown generally at U,which preferably has eight terminals, denoted respectively ||I to H8,and

may in general be like that shown at R. Here, the contact arms arepivoted respectively to the terminals |l| and ||2 and swing away fromterminals ||3 and ||5 into engagement respectively with terminals ||4and H9, both of which latter are unconnected in the present network, theactuating winding being connected across terminals ||1 and ||8. Thecontact arm terminal at lll, when the relay is unenergized, engagesterminal H3 to supply current to conductor 580 which leads therefrom tothe contact arm terminal of plaque 53. The first and second terminals ofthe latter are connected by way of la common conductor 53| to the rstand second terminals of the plaque 52 which when engaged by the contactarm of plaque 52 is seen to supply current for energizing the relay R.Thus, the cam |02 which actuates the commutator switch 92 has arelatively short extended periphery for holding switch 92 closed forrelatively short periods, in the several operative positions of thecontact arm on plaque 52, and is hence designated hereinafter thehold-in cam.

Trunking conductor 64 leads to one terminal of a third commutator switch93 whose other terminal is connected in parallel to the fourth and fthterminals of plaque 52. Switch 93 is actuated by a third cam on shaft99, namely, that at |03. This cam has an extended periphery of anarcuate length greater than that at |02 and is designed to supplycurrent directly to energize the relay R through con uctor 520 for apredetermined period for whic it is desired to hold the relay R closedfor light controlling purposes. This period has been empirically foundto be about six seconds. Hence, the Vcam |03 is hereinafter designatedthe six-second cam.

Trunlclng conductor 65 leads from the supply bus tothe second terminalof plaque 54 and has branches 543 and 545 which lead in parallel to thethird and fth terminals respectively on plaque 54. Conductor 540 leadsfrom the contact arm terminal of this plaque to the subject's light 26,the return from which is grounded. Conductor 540 is thus seen to beenergized in the second, third, and fth positions of the gangswitch andhas in series with it elements of adjustable resistance shownrespectively at 54| and 54|'. Knobs and dials for varying and showingthe values of these resistances are preferably procalled the photocellcam.

vided in positions to be under the control of the tester.

Trimking conductor 59 leads from the supply bus to the iirst terminal onplaque 55 and has a connection 553 leading in parallel to the thirdterminal on the plaque 55. `A conductor 559 leads from the contact armterminal to supply current to 'the lamps 22 which provide the glaringlights, the return from which is grounded. Conductor 559 is thusenergized from the trunking conductor in the first and third positionsof the gang-switch and has in series with it adjustable resistances asindicated at 55| and 55|', these resistances being likewise preferablyprovided with controlling knobs and dials on the cabinet, so that theymay be manpulated by the tester as desired.

A fourth commutator switch is shown at 94 and actuated by a fourth cam|94 that is on the shaft 99 and because it operates a photocell may beCam |94 has an extended periphery of an arcuate length that issubstantially the complement of the six-second cam, and is thus arrangedto actuate the commutator switch 94 and hold the same closed forsubstantially the same period as switch 99 remains open. From theterminals of commutator switch 94 are led a pair of conductors 94| and942. Conductor 94| has parallel connections to the anode-elements of apair of photocells designated P1 and P2 respectively. The cathodeelements of these photocells are connected respectively to the ilrst andsecond terminals of plaque 51. Conductor 942 leads to a terminal ofconductor 612 that is connected to a suitable source of direct currentE. M. F.

To provide a suitable source of D. C. potential in the network hereemployed which is substantially free from the discontinuities ofrectified alternating current, a secondary source of direct current E.M. F. is provided. To this end, trunking conductor 91 is connectedthrough a rectifier Tand a conductor 61 with one end of a potentialdivider or resistance 515 whose other end is grounded, as shown at 516,the divider having associated means for storinga charge in the form of acondenser 511, which is connected across the divider 515.

This secondary source of E. M. F. is connected to conductor 612 by wayof conductor 51|, switch blade w-2 `of switch W when in up-position,lamp 99, and conductor 519, which, while connected to ground, has apositive polarity when discharging through tube Q. To this end, thewinding of relay U is also connected to this circuit by conductor 613which leads from terminal l|1. A high resistance leak 919 is alsopreferably connected from conductor 51' to the junction with conductor612.

The energization of relay U is arranged to be automatically controlled.To this end. a suitable automatic control device is connected in thereturn trom the relay to ground. While any suitable device of thischaracter may be employed, it is preferred to employ a controlledelectron discharge device capable of passing relatively large currents,such as a power-sized tube or triode. A suitable triode of thischaracter is sold under the trade-name Thyratron." Accordingly, tube Qis shown in the relay return having its plate element connected to theterminal ||8 of the relay while its cathode is connected throughconductor 519 with a tap on divider 515 adiacent the end connected toground. The grid element is connected through resistance 51| andconductor 519 with the contact arm on plaque 51 which selects thecontrolling agency, such as the intensity of light on the photocells. v

To impress a suitable bias on the grid element of tube Q a conductor 512is connected at one end to resistance 51| and at the other to one sideof a condenser 519, the other side being connected by a conductor 514 toa point of suitable potential on the divider 515. To effect a timecontrol of the firing of tube Q, the fifth terminal of plaque 51 isconnected through a conductor 515 with a variable high resistance 514which is connected to the secondary source of E. M. F. by way ofconductor 912.

In the present network, it is also desirable to provide a by-pass aboutthe grid condenser 519. To this end, a conductor 58| in parallel withthe conductor 514 is provided, leading to a terminal engaged by theblade 10-9 of the switch W when in down-position, and h as in serieswith it a resistance 592. From the blade terminal a conductor 599 is ledto connect with conductor 512 and one side of the grid condenser 513. Aconductor 594 is connected between terminals H2 and ||1 of the relay inorder that the arm pivoted at ll2 when the relay is unenergized maysupply current through terminal ||5 by way of a conductor 595 to aterminal engaged by blade v| in down-position of another switch V, whichis two-bladed and has the terminal so engaged connected directly to oneterminal of lamp 99 which illuminates disk 99. The other terminal oflamp 99 is connected by a conductor 599 to the other switch blade 0 2.which, when in down-position, engages with a terminal connected by aconductor 599 to the conductor 51' for effecting a return through thedivider 515. A pilot lamp 99 is also preferably provided in associationwith the lamp 99 and arranged to give a signal to the tester showingWhether or not the lamp 99 is illuminated. Accordingly, the lamp 99 isconnected in parallel with lamp`99 through a conductor 5 91 which leadsfrom the terminal of the blade o| to one terminal of the lamp 99, theother side being connected by a conductor 589 to the terminal of blade v-2. A controlling resistance for the lamps 99" and 99 is also providedat 599. connected in parallel with the lamps.

Trunking conductor 99' is arranged to connect directly with the otherterminal connected by blade a-2 when in :up-position. In this position,current to illuminate the lamps 99 and 99 is supplied for trial purposesdirectly from the supply buses 59. Accordingly, the terminal engaged bythe blade v-l when in up-position is shown as connected by a conductor59| directly to ground.

Trunking conductor 59 is shown as connected directly to both terminalsengaged by blade w--4 f of the switch W. From the terminal to whichblade w-4 is pivoted, a conductor 99| is led to supply illuminatingcurrent to the lamp 99 which illuminates the background plaque in thecabinet. The other side of the lamp 99 is connected by way of aconductor 992 to ground, a controlling resistance 999 being connectedacross the terminals of the lamp.

Trunking conductor 19 is shown as connected to one terminal of therunning winding 193 of a clock K, the return from the winding 199 beinggrounded. The clock K is preferably of the so-called "stop-clock varietyand has a clutch Winding 194, the return from which is also grounded.Current to energize this winding is provided by conductors mi and.102,the former of which is tapped into the-,conductor 10 -and leads tothefthterminal of plaque 53. Conductor '|ll2 leads from the fth terminalof plaque 56 and is connected tothe otherend of clutch winding 104. Bythis arrangement,` it is seen that the energization of the clutchWinding '|04 is under the control of the relay U, the conductors lllland -||l2liaving the contactarm pvoted at terminal in series therewithfor completing the circuit in the fifth position of the gang-switch byway of conductors 530 and The construction of the commutatorV switchillustratedin 9Iis seento involve `theprovision' of'. a vbase .9|0 whichsupports a revolvable insulating member .9H to which is lsecured 1anactuating arm 9|2.` The member 9| Ihas a conducting segment -9|3 onwhich. bear contacting terminal membersl and SI5 arranged to beinsimultaneous engagement for one position. of the arm SI2 and at leastvone of them out or engagement in another position; The arm 9|2 is, ofcourse, biased'to hold the contact member. 9|3 normally in opencircuit'positionand when actus ated to move the same to a circuitclosing position. A-housing (not shown inthe interests oi' clearness' ofillustration in the drawings) is preferably provided seating onthe baseand arranged to enclose the-mechanism here shown.

Operation In operation, the subject to be tested'is seated adjacent thecabinet l0 so `that vhernaylook through the eye-shield at I2 in the rstinstance, and the procedural ysteps lior testing'lhis several visionsensitivitiesA administered.

Preparatory to administering the testsv for glare blindness 'and -glarerecovery, the .subjects accommodation tothe lights in the cabinet isascertained and the lightcalibrated. To make-the first calibration,thegangeswitch is movedto its first position, i. e., handle 50 isturns-riso that the `contactarme onplaques 5| to 5i" engagesimultaneously with the rstterminals on each of the same. In thisposition, it is seen that the glare lights at 22 are turned on bycurrent supplied through the circuit comprising conductors $6 and 5533,the contact arm of plaque 55, conductor 550, resistances 55| and 55| andlamps 22 which are grounded. Assuming now that itv is desired to havethe light from the 'lamps 22 of apredetermined value, for ex ample, 30foot-candles at the subjects eye,

the light incident upon the photocell Pr will cause current` to passfrom secondary source ci E. M. F. in the circuit comprising conductors5'52, 9552, sill, switch iid, photocell ier, the `contact arm on plaque57, conductors 510, 51|, andl, to feed va charge 'to the grid element oftube Q and condenser Sie, as soon-as switch 9S has .been closed. Toclose switch 9, the tester presses momentarily the push-button switchwhich starts the motor M. As soon as the motor starts theswitches 9| toad are moved by their" cams to' closed positions, current for-continuingthe running of` the motor being now supplied through the circuitcomprising conductors S3, 5|3, 5|0, S2" and switch 9| to the terminal ofmotor M which is grounded. 'Current to actuate relay R also is suppliedfrom conductor 63 through a circuit comprising conductors 630, |53 l,580, blade w|, 55|, the arm at IH, conductors 530, 53|, and 520, andthence tothe winding-e which is grounded. When the relay closesconductor 630 is energized directly from conductor 6L Switch 8| is nowincontrol andkeeps the motor M running. A D.'C.;component of current isalso supplied through rtrunking conductor Bland switch'lpl), wheninup-position which is utilized` when relay R opens to effect quickstoppage of the motor M without overshooting When the relay R closes,the arm pivoted at 1| swings into engagement with terminal 16 to connectthe conductor 630 directly to the trunking conductorrl. Thus, when thehold-in, switch 92' opens, there is no change in the current suppliedfor running-motor The steps voi calibration areproceeded withafter theswitchf vhas been depressed, whether vor Vnot the switchI |32v has .yetopened; .From .the arrangement, shown, it is seen that-this grid `oftube Q ismaintained at a rnega c tivevv potentialxwith respect. tol'ther-cathode element by: virtue of the kvoltage'on the resistance 51|,which serves asa current `limiting element and is given a suitablevalue, for, example, a value of about 10,000 ohms. In the circuit hereprovided, it is seen that :for-a volt, GO-cycle source, the resistance515 has across itl-approxlmately 150 D. C. fvolts as a result of therectier T which' is in-.seriesfvwith .the source of alter` natingcurrent. 1":

When the switch W'is'inthe up-position on the drawing, the 'relaycircuitv having the plate element of the. tube-Q- infserleswith it has apositive potential applied thereacross. The plate current of the tube Qand 'hence rthatjvvhich energizes the relay U is of zero'value until thegrid tires the tubeel 'I'his voccurs-when the intensity off-thelightisfsuchas to cause the condenser- 513; to be charged with sulicientpositive potential toV overcome the lnormal negative grid biaspotential: When the tube -lires, plate ,cur-,- rent is passedandcontinues to pass irrespective of the grid potential, energizing therelay U so as to swing the arms pivoted at 'Hl and ||2 and fbreak thecurrent through V'conductors 560, 56|, and 530. This deenergizesthe-relay R and Astops motor M; "Iosto'p' the passage of plate currentin the tubefQ, lthe plate or anode voltage supply connection must beopened. This is accomplished by moving blade 111-2 to its neutral ordown-position. V.

When relay R is deenergized, the contact arms pivoted at 1| and l2 openand interrupt the supply of current to the conductor $30 which is nowthe sole source 'of current 'to the motor M. The motor M stops, inconsequence, the stoppage-being quickened by the action of the D. C.componentv of currentsupplied through the device S. The strength oi'the-current Vin photocell vP1 determines the rate of charging ofcondenser 513 and hence theinst'an't at which tube Q lires. Theintensity of the lights at 22 on the photocell P1 may hence bedetermined from the travel ofthe hand 30 about its dial on the cabinet,Athe' desired travel of the hand 30 for 30 foot-candles being'known fromprevious laboratory calibration. In 'the event the hand 30 does nottravel thedesired distance but either fails short or goes past the mark,the resistances at 55| and 55|" controlling'lamps 22 may be adjustedvruntil the desired light intensity is obtainecLj` Y' To reset theapparatus for another test, the switchffW is now thrown to itsdown-position. This is seen toV discharge the condenser 513 through thecircuit comprising conductors 583, switch blade w-S, resistance 582 andconductor 53| to the other side of the condensero This discharge is seento reset the potential on the grid or tum Q while the simultaneousopening of switch blade w--2 removes the potentiel from the plate oftube Q so that the passage of energizing current through relay U isstopped and the contact arms pivoted at iii and H2 rali back to the openrelay position. setting up a circuit for energizing the relay R,provided switch W is again thrown to its up-position As a second steppreparing the apparatus to make a vision test. the light of the lamp at2l is calibrated. To this end, auxiliary push-button switch H isnrstmomentarily depressed by the tester to energize the relay R. Currentis now supplied directly from trunking conductor 6l. When the relay R isthus closed, current to operate the motor M is also supplied fromtrunking conductor 6I by way of the contact arm pivoted at 1|,conductors 630, 6l I, M0, 62", and switch BI to the terminal of motor M,the switch H0 being held depressed until the dial shows the hand 30 atits initial position when the motor cam 10i will automatically operateswitch 9| to open the motor circuit. To calibrate the intensity of thesubject's light. i. e., the light from the lamp 26, the gang-switchthrough handie 50 is moved to its second position in which each of thecontact arms engages with the second terminal on plaques 5| to 51. Inthis position of the gang-switch, no current is supplied to the glarelights 22. Instead, current is supplied through trunking conductor 65,the contact arm on plaque 54, and conductor 640 to the lamp 26. Thelight stop disk 26' is now moved by knob 21 to place its largest openingin front of the lamp 26 and the intensity oi the light projected on theobject 23 is measured by means of the photocell Pz which is now cut intothe photocell circuit instead of the cell Pi.

The tester now depresses the switch 90 to start the motor M and closethe commutator switches Si to 94, the hold-in switch 92 operating tosupply current to the motor M until the relay R closes to supply currentdirectly from the trunking conductor 6I by way of conductor B30. Thephotocell P2 operates as before when switch 9d closes to charge thecondenser 513, which, when charged suniciently, lires the tube Q so asto energize the relay U and swing the arm pivoted at il! to open thecircuit, deD ergizing the relay R. This stops the motor M as before, andthe travel of the hand at 69 over the dial is an index of the iightintensity projected by the lamp 26 upon the object 23, the properdistance which the hand should travel when light of a desired intensityis projected being known from previous laboratory` calibrations. In thisinstance, it is desired that a light intensity of about 2 foot-candlesshall obtain at the object 23. The resistances at 54! and 5M' are, ofcourse, adjusted until the desired travel is obtained. When calibrationis completed, the apparatus is brought to its desired testing positionby depressing push-button switch H0 and starting the motor M to bringhand 30 automatically to its zero position, the switch 9| automaticallystopping the motor when this position is obtained.

Variation of the subjects light may be obtained other than by varyingthe resistances 54| and 5M. This, of course, is achieved by revolvingthe disk 25 which has various sized holes or lenses which operate tomodify the light in desired steps. The light from the lamp 26 may becollected from a small area, for cxample, en area of 1/2 x 5%", andprojected through an opening in the disk 25 onto an arca which may be 6x 9" for illuminating object 23 and element 24. The openings ordiaphragm stops in the disk 25 are preferably a graded series, forexample, the stops may be ten in number, ranging in size from l/H to FA.When the first stop is operative the intensity of illuminationon object23 may be less thanl M00 loot-candles While the latter may admit lightso as to illuminate the object with an intensity of 2 foot-candles for agiven adjustment of the illumination o! lamp 26. The collecting area andthe object 23 will, of course, be conjugate foci of the lenses of thelight stop. When it is desired to know the actual illumination resultingfrom the use of any one of the light ad- Justments had from the disk26', foot-candle power measurements are made by means of the photocellP2, the intensity being determined by the travel of the hand 30.

To make a test for glare blindness, the gangswitch through its handle 30is moved to the third position and the stop disk 25' moved to thatposition, ascertained from the calibration steps, which stops thesubjects light down to a value just sufficient to illuminate the object23 with an intensity making it just visible to the subject when the lamp26 is on. Current to illuminate the lamp 26 is supplied throughconductors 65 and 543 to the arm of the gangswitch and thence byconductor 540, resistances 64| and 64I to the lamp 26 which is grounded.Current for illuminating lamps 22 is supplied in the same manner as whencalibrating them,-

i. e., through the circuit comprising conductors 66, 663 and 560 andresistances 551 and 55V to lamps 22 which are grounded.

Light from the lamps 22 is now projected into the subjects eyes and theblindness produced thereby prevents his seeing the object 23. The testernow rotates the stop disk 25' by maniputhe object 23 had from thesubject's light. The tester also manipulates knob 28 to rotate theelement 2li and asks the subject to tell him the direction of the linesthereon as soon as the subject perceives the same. As soon as thesubject announces this fact, the correctness of which is verified by thereading of the position of the markings shown by the knob 28, the testernotes the degree in illumination had from lamp 26 in order to get thisresult. This amount in illumination is taken as a measure of the sup-;lect's glare blindness.

To make a test for glare recovery, the gang-1 switch is moved to thefourth position and the apparatus checked to ascertain that switch 80 isclosed and switch |00 is in its up-position. The movement of thegang-switch to the fourth position is seen to extinguish the light fromlamps 22 and 26, their illumination being now automatically controlledby the circuits set up by the fourth Aposition oi the gang-switch. Thesubject is again directed to watch for the appearance of the object andto signal when he ascertains the direction of the lines on element 24 byopening switchv 80 and announcing the direction of the lines perceived.

The test procedure is started by depressing switch SD. Motor M, inconsequence, is started, and the cams iiii to itt actuate the commutatorswitches si to 94 inclusive. The closing of switch 6l suppliesalternating current by way of conductor jtm to operate the motor IVI.This .lating knob 21 to increase the illumination of is seensimultaneously to short circuit rectiiier S so that the D. C. componenthad from the trunking conductor 62 ceases. The motor circuit supplyingthe A. C. current comprises conductors 6|, 6|', switch blade 80',conductors 5|4, 5|0, 62", switch 8|, and motor M, which is grounded.When switch 8| is closed by cam |0I, automatic controll of the motor Mis thereby taken over. which insures its continuous running for thecycle of the test, namely, a period of twenty seconds.

At the instant when the switch 80 is closed, the subjects light 26 isilluminated by means of a circuit comprising conductor 6|, the relay armat 12, conductor 130, switch blade 80, conductors 544, 648, resistances54| and\.54|', and lamp 26, which is grounded. Cam |03 when turned,

by the motor M causes switch 83 to close for six seconds. While switch93 is closed, current is seen to energize the relay R through a circuitcomprising conductor 64, the fourth terminal on plaque 52, and conductor620, and thence to the 'winding e,. which is grounded. 'Ihe energiza.-tion of winding e causes the relay to close, the arm at 12 swinging awayfrom terminal 13 and breaking the circuit supplying illuminating currentto lamp 26 and coming into engagement with terminal 14. In thisposition, which obtains for the six seconds for which switch 83 isclosed, current passes to illuminate the lamps 22 through a circuitcomprising conductor 6|. terminal 14, conductor 634, the fourth terminalof plaque 55, conductor 550, resistances 56| and 55|', and lamps 22,which are grounded. At the end of the six seconds, the relay R isautomatically deenergized by the opening of the switch at4 83, and therelay arm at 12 falls again into the open relay position engagingterminal 18 to close the circuit which reestablishes the supply otcurrent to the lamp 26. The blindness temporarily produced in thesubjects eyes by the glare from lamps 22 prevents his seeing the objectat 23 when the lamp at 26 is reilluminated. Motor M, however, continuesrunning and the sub.- iects eyes gradually accommodate themselves to thecondition of illumination on the object 28. As soon as the subject seesthe object at 23, he opens switch 80. The fact that he actually sees theobject can be checked by the correctness of his designation of thedirection of the lines on element 24. As soon as switch 80 is opened, itis seen that blade 80 breaks the circuit supplying current to the motorM, its stoppage without overshooting being substantially insured by theD. C. component of current supplied through conductor 62. The periodrequired for recovery from glare can hence be ascertained by thepcsition of indicator hand 80 on the dial. It will be noted that blade80" also opens the circuit supplying current to lamp 26 to prevent thesubjects seeing the object after he has give the signal and announcingthe direction of the lines later ascertained in order to get a betterscore.

To make a test for movement sensitivity, the gang-switch is retained inits fourth position, but switch is moved to its down-position, theswitch 80 being again closed, which illuminates the lamp 28 through thecircuit comprising conductors 6|, 6|', switch blade 80', conductor 6|4,and lamp 28, which is grounded. v

In this test, the subject is instructed to look at the small white body3| and signal when he perceivesV its direction of motion by openingswitch 80. It lamp 26 is also turned on by this switch, the intensity ofiight therefrom may be modiiied by the tester, as desired, by turningknob 21. 'Ihe tester also moves switch |08 to engage with one or theother of the terminals |01 and |08 which determine the direction inwhich the motor N revolves and hence that of the movement of the body3|.

When all is in readinessfor the test to begin, the tester depressespush-button switch |06. Alternating current to actuate motor N is nowsupplied, through a circuit comprising conductors 6|, 6|'. switch blade80', conductors 5|4 and |0, terminals 83 and 82, by-pass conductor 86,conductor 86', and iield winding 81, which is grounded. The closingofthe switch |08 permits the passage of out-of-phase current through oneportion of the secondary 91 and the shading windings 86, which causesrotation in a desired direction of the armature a and the cam disk |05.This cam disk operates commutator switch 85 to close the main circuit tothe windings 81 independently of the by-pass, i. e.. from terminal 82 byway of conductor 85. switch 85, and conductor 86'. The rotating armatureimparts m0- tion through the gearing at 84 and shaft 38 to the carrierdisk 82, which causes body 3| to move slowly. As soon as the subjectperceives the direction of motion he opens the switch 80, the switchblade 80', breaking the circuit supplying current to the motor N, thesubject announcing the direction of movement which he perceives. Thedirection announced may be checked by the position or hand 35 on itsdial and also bythe position of switch |08. A

When the motor .circuit above described is closed, the. circuit of therectifier S through conductor 84 is shorted so that no'D. C. componentof current is passed while the motor circuit sup-l plying motor N withrunning current is closed. Upon the opening or the motor circuit, thisshort is removed and the D. C. component of current supplied byconductor 62 then passes and brings about the sudden stoppage of motorN'. preventing its overshooting. The position of hand 85, in

consequence, indicates additionally the period of time required by thesubject to ascertain the direction oi motion of body 3|. This period maybe read directly from the dial, provided the hand is on the zero pointo'i' the dial at the instant the test began. The reciprocal of thisperiod is taken as a measure of the subjects sensitivity to motion.

To make a test lfor speed of perception, the gang-switch is moved to itsiitth position while vthe subject is requested to look at the scenethrough the screen at I5 and watch for an object that may momentarilyappear thereon. Both switches V and W are moved to down-positionspreparatory to this test. Blade w-8 contacts with the terminal oiconductor 58| to eect the dischargel of condenser 513V while blade w4closes a circuit through the lamp 38 comprising conductors 68, 88|, lamp38, and conductorl 882, which is grounded. Lamp 88 illuminates thebackground scene of plaque 86. The other blades of switch W are seen tobe on dead terminals.

'I'he switch V in the down-position is seen to set up a circuit forilluminating the lamp 88 and pilot lamp 88, the source of E. M. F. beingthe secf the relay arm pivoted at H2, conductors 584. 613,

61|, the switch blade w-2, and conductors 518 and 516 and thence toground. This circuit is blade v-l to blade v-Z by way of conductors 081and 588. Current passes in the lamp circuits when closed by switches Vand W, until the closing of the relay U, which takes place when the tubeQ is fired.

The rlfth position of the gang-switch sets up a circuit for operatingthe motor M from current f supplied through the hold in switch 92. Acircuit through switch 03 is also set up to energize the relay R. Thesubjects light 2l is also seen to be supplied with current through thecircuit including trunking conductor B5.

In this fth position, circuits for actuating the stop-clock K are alsoset up. The iirst of these circuits comprises conductor 10 and runningwinding 103 which is grounded. Clutch winding 104 when energized causesthe hand of the clock to move, this Winding being ,in a circuit tappedinto conductor 10 and comprises conductor 10| leading to the filthterminal of plaque 53, and thence by conductor 530 to terminal ||0 ofrelay U, and thence by conductor 58| to a terminal engageable by bladew-l of the switch W. From this blade, the circuit is continued by way ofconductors 500 and 102 to the clutch winding 100 which is grounded.

The firth position of the gang-switch also sets up a circuit for thecharging of condenser l1! by connecting the conductors 812, 61|, and 010through the ilfth terminal on plaque 51 to the conductor 510 which isconnected through resistance 51| to the grid of tube Q and in parallelto a terminal of condenser 513 through conductor 512, whereby thecondenser may be charged with rectified current from the trunklngconductor 01 provided the condenser is not shorted by the switch bladew-I.

If now switch W be thrown to the up-position, clock K starts running andcondenser 513 starts charging by reason of the opening of the dischargecircuit by the blade w-I. Throwing the switch W to the up-position isseen to extinguish -the lamp l0 but momentarily, since, as soon as theblade u 4 reaches the up-position, it establishes contact with anotherterminal tapped into conductor 60. The background lamp 38 is thus seento be maintained in an illuminated condition whether the switch W be inupor down-position.

Current to illuminate the lamp 00 passes simultaneously until the relaycloses from the secondary source of E. M. F. across divider 51B througha circuit comprising conductors l1', |80, blade v2, conductor 500, lamp80, blade v-I, conductor 585, the relay arm pivoted at H2, conductors584 and 61|, to a terminal adjacent switch blade w-2 of the switch W,and thence by conductor 510 to ground.

The period, for which lamp 88 remains illuminated and for which clock Kruns, is determined by the time constant involved in the charging ofgrid condenser 513, this condenser being charged through the adjustableresistance 014 which has any suitable value. for example, 3 megohms. Insuch case, the condenser 513 may have capacitance of a value of from .1to 1 microfarad. When the tube Q fires, the relay U is energized andswings the arms pivoted at and ||2 so as to break the clock circuit andthe circuit which illuminates lamp 80. While the time for which the lampis illuminated may be read.directly on the dial of the clock K, this Iperiod is determined by the setting of the mova' able tap on theresistance 814. 'I'he dial for this. resistance on the cabinet may hencebe gradu ated to read time-periods since its various set tings determinethe period for which the lamp 00 is at any time illuminated. 'I'he clockK is thus seen to be needed only for purposes of calibration and i'sadvantageouslydisconnectably associated with the mechanism of cabinetl0. The several other circuits set up by the gang-sv switch in its tlfthposition are advantageously employed to set and check the position ofthe hand I0 moved by the motor M in the glare recovery test. For thispurpose, the switch |00 is moved to the up-position. 'ro make thischeck, push-button switch so is depressed to start the motor M. 'I'heswitch at l), 92 is seen to supply current through the trunkingconductor 63 and the iifth terminal of plaque 5| to the motor M by wayof conductor 510 for a period suiliciently long to permit the relay R toclose. Current for energizing the relay is supplied through trunkingconductor 04 and the sixsecond switch 03 to the iifth terminal on plaque52 and thence by way of conductor 520 te energize the relay R and itswinding e, which is-A grounded. Current to continue the running .01"30the motor M is supplied by way of conductors 0| and |30 to the fifthterminal of plaque 5| as soon as the relay closes. Switch 0,2, which isactuated by cam |02 which has `a very short engaging periphery, is seento open after the 35 4closing of the six-second switch 03. The runningof the motor continues only as long as the relay R continues closed.When six seconds have elapsed, switch 83 opens and the relay isdeenergized. The lcontact arm pivoted 4at 1| breaks 440 the motorcircuit and the motor M is stopped without overshooting by reason of theD. C. component supplied by way of conductor 02, rectifier S, and switch|00.

To have a direct time reading on the dial traversed by the hand'30showing accurately the period required for recovery from glare, it isdesired that the hand 30 start from the position marked Zero at theinstant the relay R opens and motor M stops when making this check. 50In the event that this is not found to be the case, the hand may beadjusted, or, ii readings have been previously made, then these may becorrected by the error round by such check.

The test for tunnel vision is administered to the subject while seatedat the closed end of the cabinet, the degrees of displacement from theline of vision for sensitivity to objects on the side being read fromthe scales on the board 0|.

To make a test for visual coordination, the subject is seated at somedistance from the open end of cabinet ||l and made to look at a pointsource of light. The Maddox rod is then held before the subject androtated before one eye and the degrees of image displacement from themeridian noted in the usual manner. If the subjects coordination isperfect, only one point of light is seen at all times. If the subjecthas a when the pins are illuminated. Several scores are generallydesirable, made for the subject when at different distances from thecabinet. 'I'his illumination may be had from the lamps i8 whichalsoilluminate charts I1. While still seated at this end of the cabinet, thesubject is tested for-visuaf keenness and astigmatism for the two eyesseparately, in the manner above indicated, by means oi the charts at I1;the last test being administered to the subject while seated or standingat the side of the cabinet so as to read the chart at 20. These lasttests may be administered to the subject when desired to obtain severalscores at diilerent distances from the cabinet.

Thus, by the present procedural steps and the .apparatus hereinprovided, the data and score for subjects as to their several visionsensitivities, which are desired and which may be deemed involved whenoperating a motor vehicle, are had in a clinical fashion and in a mannerpsychologically approved.

Since certain changes in carrying out the construction above set forth,which embody the invention, may be made without departing from itsscope, it is intended that all 'matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. In apparatus for ascertaining a desired set of vision sensitivities.of a subject, the combination with a cabinet provided interiorly withunder external control for illuminating said field, of index means forindicating the setting of said external control, ,window means in saidcabinet through which the subject may view saidileld, 40 lightgenerating means for conditioning the subjects eyes, additional meansfor giving a testing light stimulus, and means for ascertaining the`subjects optical reactions.

means for simulating a ileld of vision and means l 2.In apparatus iorascertaining a desired set of vision sensitivities of a subject, thecombination with a cabinet provided interiorly with an artificial scenesimulating conditions that may be encountered in night driving togetherwith means simulating the lights from a subjects veh icle forilluminating said scene, of eye-shield means through which the subjectmay view saidA A scene, means including an index controlled lampemitting light adjusted to predetermined intensity simulating a glaringlight that may be encountered on a road for producing temporaryblindness in the subjects eyes, additional means to be perceived by thesubject associated with the scene, means for adjusting the illuminationof said additional object, and means for ascer- 00 taining the amount ofadditional illumination required to overcome the subjects temporaryblindness.

3. In apparatus for ascertaining a desired set oi vision sensitivitiesoi a subject, the combina- 05 tion with a cabinet provided interiorlywith an artiilcial scene simulating conditions encountered whenoperating a motor vehicle on a high. way together with means forilluminating the scene simulating the lights from the subjects 70vehicle, of eye-shield means through which the subject may view saidscene, means for projecting glaring light into the subjects eyes for aperiod oi adjustable length, an additional object associated with saidscene to be perceived by the 75 subject, meansior illuminating saidadditional object with light of an intensity that may be varied, andtiming means for ascertaining the period required for the subject toovercome the temporary blindness produced by the glaring light projectedinto his eyes.

4. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with a cabinet provided interiorly with ascreen having a scene simulating that obtaining on a highway'whenoperating a motor vehicle at night, of means within said cabinet forprojecting light upon `said scene to illuminate the same simulating thelight from the subjects vehicle, eye-shield means in the cabinet throughwhich the subject may view said scene, index adjusted light projectingmeans associated with said screen simulatingglaring lights from a.vehicle on a highway, an additional object associated with said scene ina position to be seen by the subject, a directional element associatedwith said additional object arranged to be illuminated with said objectfor checking the subjects perception of the same, means forrelativelydetermining the amount of illumination on said additional object, andmeans for timing the reaction oi the subjects eyes in perceiving saidadditional object under predetermined conditions of illumination.

5. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with a cabinet provided interiorly withmeans for simulating a ileld of vision and means under external controlfor, illuminating said field, of eye-shield means in said cabinetthrough which the subject may view said ileld, an object arranged forcontrasting illumination on said neld. means for imparting relativelyslow lateral motion to said object, an indexl out of the subjects viewfor showing the direction of said lateral motion, and means forascertaining the period required by the subject for perceiving thedirection of said lateral motion. 4 l

6. In apparatus for ascertaining a desired set of vision sensitivitiesot a subject, the combination with a cabinet provided interiorly withmeans for simulating a neld of vision, of eyeshield means in saidcabinet through which the subject may view said ileld, said fieldincluding a relatively dark rotatable disk mounted for movement about anaxis horizontally disposed, a relatively small white body mounted onsaid disk near its periphery, means for imparting relatively slow rotarymotion to said disk in either direction, an index out of the subjectsview for showing the direction of said lateral motion, and timing meansfor measuring the period required by the subject to detect the directionol motion imparted to said body.

'1. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with a cabinet provided interiorly withmeans for simulating a ileld of vision, of eyeshield means in saidcabinet through which the subject may view said -eld, means for placingan object on said field in randomV positions, index means on theexterior of the cabinet for showing which of said positions is selected,and means for illuminating said ileld and object for a transitory periodof relatively short duration, and means for ascertaining the period forwhich said illumination obtains.

8. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject. the combination with a cabinet provided interiorly withmeans for simulating a neld of vision and means under external controlfor illuminating said field,

Aist

of eye-shield means in said cabinet through which the subject may viewsaid heid, said ileld including a background scene, a movablediscernible object out oi said ileld, and means for projecting saidmovable discernible object into the subjects field ci view, index meanson the exterior of said cabinet for showing the position of saiddiscernible object, independent means for illuminating said discernibleobject for relatively short periods, and means for measuring the periodfor which said illumination takes place.

9. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with av cabinet provided interiorly with abackground scene simulating a condition that may be encountered on ahighway, of eye-shield means on said cabinet through which the subjectmay view said scene, a transparent member disposed in said cabinetobliquely to the line of vision in front of said scene, a rotatable diskin said cabinet having an object whose reflection may be projected bysaid transparent member into the subjects eyes in a manner such thatsaid object appears to be in said scene, index means on the exterior ofsaid cabinet for controlling and indicating the rotation of said disk,means aiiording relatively low continuous illumination of said scene,means for transitorily illuminating said object, and means forautomatically determining the period ior which said transitoryillumination takes place.

10. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with a cabinet, ci a disk mounted thereonfor viewing at a distance and adapted for rotation about the horizontalaxis, a plurality of contrasting bodies mounted at various distancesfrom the face of said disk, and index means on the exterior of saidcabinet ior rotating said disk at will.

11. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with a cabinet provided with a visiontesting field to be scanned by the subject, oi a background diskrotatably mounted in said cabinet adjacent said eld, said disk having ahorizontal axle. index means on the exterior o! said cabinet forimparting motion at will tosaid axle, a plurality oi objects adapted tobe contrastingly illuminated mounted at varying distances from the faceof said disk adjacent the periphery thereof, and a common means forilluminating said objects and said eld.

l2. In apparatus ior ascertaining a desired set of` vision sensitivitiesoi a subject, the combination with a cabinet provided interiorly withscreen means artiflcally simulating the condition on a highwayencountered in the night driving of a motor vehicle, of means in saidcabinet for including a lamp projecting light o! variable intensity uponsaid screen in a manner simulating the light from the head-lamps of thesubjects vehicle, eye-shield means in said cabinet through which thesubject may view saidscene, means including a lamp on said screensimulating glaring headlights of a vehicle on a highway, an additionalobject on said screen adapted for illumination at the side of saidglaring headlights, an electric network having switching meanscontrolling the supply of currentA to said lamps, and a motor connectedto actuate said switching means and adapted for timing the re- 'actionsof the subjects eyes to the light selectively projected by said lamps.

13. In apparatus for ascertaining a desired set of vision sensitivitiesof a subject, the combination with a cabinet provided interiorly with ascreen artificially simulating conditions encountered on a highway whenoperating a motor vehicle at night, oi a light projector within saidcabinet for illuminating said scene having an electric lamp and anadjustable light stop, light projecting means having lamps associatedwith said screen in a manner simulating a vehicle on a highway at night,an additional object on said screen having an element movable at willarranged for illumination at the side of the light projecting means onsaid screen, a second screen above the rst-named screen having anopening, a light object arranged to be perceived in said opening, arelatively dark disk carrying said object near its periphery. areversible motor for rotating said carrying disk and imparting slowlateral movement to said object, an electric network for supplyingcurrent to said lamps and said reversible motor. switching means forsetting up circuits and controlling said lamps and said reversiblemotor, and a second motor controlling said switching means and timingthe periods for which selected lamps are illuminated.

14. In apparatus for ascertaining a desired set oi vision sensitivitiesoi a subject, the combination with a cabinet provided interiorly with ascreen artiiicially simulating conditions encountered on a. highway whenoperating a motor vehicle at night, or a light projector within saidcabinet for illuminating said scene having an electric lamp and anadjustable light stop, light projecting means having lampsA associatedwith said screen in a manner simulating a vehicle on a highway at night,an additional object on said screen having an element movable at willarranged for illumination at the side of the light projecting means onsaid screen, a second screen above the first-named screen having anopening, a light object arranged to be perceived in said opening, arelatively dark disk carrying said object near its periphery, areversible motor iorrotating said carrying disk and imparting slowlateral movement to said object, a third screen adjacent said secondscreen having a tachistoscope comprising a scene and an objecttransitorily appearing thereon at random, a lamp for illuminating saidtachistoscopic object for rela-l tively short determinable periods, anelectric network ior supplying current to said lamps and said reversiblemotor, manually operable switching means in said network for settingupcircuits'coordinating the lighting of lamps and stimuli to be given,automatic switching means for determining the periods for which thelamps and stimuli are to be operated, a second motor for actuating saidautomatic switching means having means for indicating the periods oitime i'0`r which it runs, and means for precisely determining theduration of said tachistoscopic illumination. HARRY R. DE SILVA.

